Grant's fellow Swede Soderberg led by eight shots going into the final round, but his advantage shrank to four shots at the turn on Sunday after a shaky front nine.
As 2022 champion Grant turned up the pressure with a perfect 65 in the final round, Soderberg made more mistakes on the back nine, bogeying the 13th and 15th holes to cut his lead to one shot with one hole left.
Then things went from bad to worse for the overnight leader, who three-putted from 25 feet on the 18th green, ruining his chances of winning outright and missing the playoffs.
Home hero Grant, who had been preparing for a possible playoff, suddenly found herself in the winner's circle and proved her superiority with a total score of 17 under par to claim another victory in a tournament that saw 78 men and 78 women competing for a share of the prize money and a trophy.
Soderberg finished with a 77 to tie for second at 16 under with Scotland's Callum Hill, while Swedish Ladies European Tour star Joanna Gustafsson was three shots back in fourth with Britain's Alex Fitzpatrick and Andy Sullivan.
On the fourth day, Grant performed well, grabbing four birdies in five holes starting from the second hole to narrow the gap.
“I'm so surprised. To be here and be the hometown champion again. It's awesome.” – Lynn Grant.
The 24-year-old took aim at the ninth hole with a 6-foot birdie, then holed out from 15 feet at the 10th for two consecutive birdies.
She gave herself more chances down the stretch, but it wasn’t until the 18th hole that she finally holed out for birdie.
“I'm so surprised,” Grant said. “To be here and be the hometown champion again is awesome.”
“To be honest, I just wanted to go out and give myself a chance today. I didn’t even think I had a chance of winning – 11 shots is a huge gap.
“So I just want to go out there, have fun and make as many birdies as I can.
“Just having fun playing ball at home with my brother.
“It’s just been an incredible day.”
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